I've lived in Portland for 28 of my 30 year life, and I completely adore Seattle. I make at least 3 trips a year to the Emerald City and wish I could make more.
The cities have different vibes, I think. I love the big city feel of Seattle, and I love the coziness of Portland. Though Seattle is touted as being very "indie" and "arty" I actually think Portland is more so. Obscurity and originality abound in Portland where in Seattle it seems more contrived. I love that Seattle has the Seahawks, Mariners, Huskies and to a lesser degree the Sonics. Just having that many "big" programs adds a sense of excitement to Seattle that Portland just doesn't have. The restaurants in Portland, surprisingly, I think are better, but that might be because I'm more familiar with my hometown.
The Women. Don't get me started. For those of you trashing Seattle women, stay out of the gay bars.

There are WAY more attractive Women in Seattle than Portland, even though for Portland's size, there are quite a few. Either way, neither City lacks good looking girls. Portland probably has more strippers so that inflates out numbers a bit.
Traffic is worse in Seattle, but not by a lot.
To "hate" Seattle just seems ignorant to me. To echo what Ed said above, I really don't think people in Seattle think much about Portland so there's no reason for us to think much of them. Just enjoy each others cities for what they offer and enjoy the differences!